β‐Ionone reactions with the nitrate radical: Rate constant and gas‐phase products

Abstract

The bimolecular rate constant of k N O 3 ·+β-ionone (9.4 ± 2.4 × 10 −12 cm 3 molecule −1 s −1 was measured using the relative rate technique for the reaction of the nitrate radical (NO 3 •) with 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one (β-ionone) at (297 ± 3) K and 1 atmosphere total pressure. In addition, the products of β-ionone + NO 3 • reaction were also investigated. The identified reaction products were O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine and N,O-bis(trimethylsilyl)trifluoroacetamide were used to propose the other major reaction products: 3-oxobutane-1,2-diyl nitrate, 2,6,6-trimethylcyclohex-1-ene-carbaldehyde, 2-oxo-1-(2,6,6-trimethylcyclohex-1-en-1-yl)ethyl nitrate, pentane-2,4-dione, 3-oxo-1-(2,6,6-trimethylcyclohex-1-en-1-yl)butane-1,2-diyl dinitrate, 3,3-dimethylcyclohexane-1,2-dione, and 4-oxopent-2-enal. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible β-ionone + NO 3 • reaction mechanisms based on previously published volatile organic compound + NO 3 • gas-phase mechanisms. The additional gas-phase products 5-acetyl-2-ethylidene-3-methylcyclopentyl nitrate, 1-(1-hydroxy-7,7-dimethyl-2,3,4,5,6,7-hexahydro-1H -inden-2-yl)ethanone, 1-(1-hydroxy-3a ,7-dimethyl-2,3,3a ,4,5,6,-hexahydro-1H -inden-2-yl)ethanone, and 5-acetyl-2-ethylidene-3-methylcyclopentanone are proposed to be the result of cyclization through a reaction intermediate. glyoxal (HC( O)C( O)H), and methylglyoxal (CH 3 C( O)C( O)H). Derivatizing agents

Prediction of Rate Constants for Gas‐Phase Reactions of Nitrate Radical with Organic Compounds: A New Structure–Activity Relationship

“…[j] Ref. [77], rate constant re-evaluated with k limonene = 1.21 10 À11 cm 3 molecule À1 s À1 [68,70,71] at 298 K. represented. For these compounds, 92 % of the rate constants are reproduced within a factor smaller than two.…”

Rate constants for the gas-phase reactions of nitrate radicals with geraniol, citronellol, and dihydromyrcenol

“…than the measured nitrate radical rate constants for these terpene alcohols. This observed ratio (k OH • /k NO 3 ) seems to correlate with other measured terpenes such as α-terpineol (11.9), β-ionone (12.6), limonene (13.4), sabinene (11.7), α-pinene (8.5), and 3-carene (9.7) [9,15,20,21,29]. This rough approximation may be used as crude estimation of nitrate radical rate constants for structurally similar species; however, this approximation should be used cautiously as observed in the case of dihydromyrcenol.…”

“…f Jones and Ham [21]. g Harrison and Ham [20]. than the measured nitrate radical rate constants for these terpene alcohols.…”

“…The experimental procedures for determining the geraniol, citronellol, and dihydromyrcenol + NO 3 • reaction kinetics were similar to those described previously [20,21].…”

“…Experiments to measure the gas-phase rate constant of the NO 3 • with geraniol, citronellol, and dihydromyrcenol were conducted with a previously described apparatus [20,21]. A brief description is provided here.…”